The commentary considers an objection: if ‘Ḥātim’ is used to mean a different generous person, or ‘Abū Lahab’ is used for some other wicked person, the expression may be transferred away from its conventional bearer. Such a use can be closer to metaphor (استعارة) than to an ordinary allusion.
Examples:
«جَاءَ حَاتِمٌ» — reporting the arrival of the actual bearer is ordinary proper-name reference.
«جَاءَ حَاتِمٌ» — calling a different generous man ‘Ḥātim’ can involve metaphorical similarity.
«أَبُو لَهَبٍ فَعَلَ كَذَا» — if it concerns the established bearer, both straightforward identification and an additional allusive suggestion may be considered.
The same surface expression can receive a different classification when the intended referent and context change.